1. Technical Field
The present disclosure relates to a relief valve, and, more particularly, to a hydraulic relief valve including a check valve in a damping chamber.
2. Discussion of the Related Art
A relief valve controls fluid pressure in a system, such as a hydraulic circuit. A relief valve may be used in a system for hydraulic controls, such as in the aerospace industry. In addition to oil, a relief valve may be used in a system carrying other liquids or gas, such as steam.
Pressure can increase in a system as a result of process upset, and/or instrument or equipment failure. Excess pressure build up may be relieved by causing the fluid to flow through an auxiliary outlet out of the system to, for example, a hydraulic tank.
A relief valve opens at a predetermined fluid pressure, for example, based on the design constraints of equipment being protected by the relief valve. This minimum pressure is referred to as the valve cracking pressure. A relief valve may be designed to open at a predetermined cracking pressure.
A relief valve may include a spring attached to a poppet, which provides a force on the poppet to maintain the relief valve in the closed position. Once the cracking pressure is achieved, the poppet is unseated and opens, compressing the spring. When the pressure of the flow traveling through and on portions of the relief valve decreases, for example, to less than the cracking pressure, the relief valve closes to prevent further flow through the valve.
The speeds at which a relief valve opens and closes are important for increasing fatigue life of a hydraulic system. For example, a fast opening relief valve limits high pressure pulses in the hydraulic system, and a slow closing relief valve provides valve stability.
Accordingly, there is a need for a valve construction that permits a relief valve poppet to open relatively quickly, and to close at a relatively slow rate.